1. Field of the Invention
This invention relates to a high density, hermetically sealed, multi-chip package, and more particularly to a hermetically sealed, multi-chip package suitable for military and space applications.
2. Description of the Prior Art
Certain applications, such as military and space applications, require integrated circuit packages to be hermetically sealed by means of glass, or metal, or ceramic, or a combination thereof. In the prior art, each chip is individually encapsulated for such applications. A number of integrated circuit chips are typically mounted on a printed wiring board, which mechanically supports the integrated circuits themselves and provides electrical connections to them.
For commercial applications, the prior art has recognized that integrated circuit chips can be spaced closer to one another on a printed wiring board if the chip die itself is bonded directly to the board; that is, a die without an enclosure or carrier. In this prior art packaging technology, each chip is then encapsulated with an epoxy resin to protect the die and its connecting wires. This packaging technology, known in the art as chip-on-board (COB) technology, allows the chips to be closely spaced from one another on the board, and thus provides a package with a high component density. However, this prior art chip-on-board packaging technology does not provide a hermetic seal for the chips (e.g. semiconductor integrated circuits or hybrid circuits) and therefore has not been adopted for applications where such a hermetic seal is a requirement.